دانلود رایگان مقاله انگلیسی تست های بارگذاری فونداسیون سطحی بزرگ مقیاس در خاک رس نرم - الزویر 2018

abstract

This paper presents field test data from four instrumented rigid square pad foundations on soft clay that were brought to failure under concentric vertical loading. The test programme comprised two unconsolidated undrained (UU) foundation tests as well as two consolidated undrained (CU) tests. In the latter case the two foundations were preloaded to a proportion of the UU capacity and the soil was allowed to consolidate before being brought to undrained failure. In this paper, the site works and testing procedures are presented along with the load- and time-settlement responses of all four foundations. Horizontal stress and pore pressure data are presented for the two CU tests. The undrained and consolidated undrained load-settlement responses are shown to agree well with theoretical and numerical predictions. Results from the UU tests were the subject of a prediction exercise, summarised in a companion paper presented in this special issue.

5. Conclusion

A programme of large-scale instrumented shallow foundation field tests investigating the undrained and consolidated undrained load-settlement response and ultimate capacity under vertical centric loading has been carried out at the Australian National Field Testing Facility (NFTF) for soft soils. Site works and activities in preparing the tests are presented along with load- and timesettlement observations to failure. The load-settlement response, ultimate capacity and failure mode of the two unconsolidated undrained tests agreed well with each other providing confidence in the construction and testing procedures and the uniformity of the site over the area of the tests. The successful consolidated undrained (CU) test indicated an increase in bearing capacity due to the preload and consolidation phase, which was well predicted by a critical state based framework. The load-settlement response and ultimate limit state of the unconsolidated undrained tests (UU) were shown to be well predicted by numerical analysis using a simple elastic perfectly plastic constitutive model. Comparison of the observed and predicted load-settlement response were the subject of an international prediction exercise, the results of which are presented in a companion paper in this special issue.

The programme of field tests presented in this paper adds to a sparse database of large-scale shallow foundation tests on soft clay on sites with extensive site characterisation. Such studies provide an essential benchmark for assessing techniques and methods for deriving stiffness and strength parameters, available constitutive models and available prediction methods for shallow foundation response. Field testing provides an invaluable and convincing means of assessing analytical and numerical methods of predicting shallow foundation response.